Why do flags age away?
What do the words "no one" refer to? Who handle flags? Is it moderators?
How much "time" is "allowed by the system"?
In this case, a flag to close a question, it's handled by users with 3,000 or more reputation in the Close Votes review queue. It's quite full, 170 questions (though nowhere near Stack Overflow levels) and that means that for some questions the review never gets completed. Even though there may be enough active reviewers, if the decision to close a question or leave it open is difficult, some of them may skip the review.
Close votes and close flags age away after 4-14 days - if you're certain the question should be closed, you can flag again. Otherwise, it's better to leave it open; the worst thing that can happen is that it gets an answer :)